The present invention relates in general to threaded closures for drums and similar containers. More particularly, the present invention relates to a replaceable, threaded closure for plastic drums wherein the closure is crimped to the drum neck and a removable plug closes the central opening of the closure. The closure is designed to be replaced such that the drum filler on reconditioner is able to replace the closure when the threads become damaged.
Plastic drums of the type with which the present invention closure will be used generally include a two-inch, buttress-threaded opening and a two-inch straight (standard) pipe-threaded opening. From a strength and reliability standpoint, the butress-thread opening is preferred for plastic drums. With such an opening, it is relatively simple to overcome cold flow and other characteristics of plastics in order to provide an opening/closure combination which seals easily and passes the required drop and hydrostatic pressure tests.
The presence of a two-inch straight pipe thread opening as one of the two drum openings presents a different set of concerns from those of the buttress-thread opening. The cold flow characteristics of plastics and the ease with which plastics expand and contract during cooling after processing creates a number of problems for container and closure fabricators. Concerns over tolerance variations, shrink and warpage must all be addressed when plastics are used for the drum and the drum openings. Another concern with the use of a two-inch straight pipe thread is that after it is molded, it is not as strong as the buttress thread opening simply because there is not the same mass of plastic present in the individual threads.
A further concern with the use of plastic for the two-inch straight pipe thread opening is that it is relatively easy for the end user of the container to cross thread a metal pump or valve into the two-inch opening and as a result ruin the entire drum as far any any refilling or redistribution is concerned. One possible solution to this problem is to put two buttress-thread openings in the drum, in essence replacing the two-inch straight pipe thread with an additional buttress thread. However, this revision, while possible, is generally regarded as being unacceptable because there is very little buttress-threaded dispensing equipment in the field. Consequently, while the two openings are needed for filling and dispensing, wherein one of the two openings serves as a vent, the thread styles of these two openings must take into consideration field use. Since the dispensing equipment in the field normally incorporates a two-inch straight pipe thread, that thread style must be provided as part of one of the two drum end openings.
The present invention allows the drum filler as well as the reconditioner to replace the closure which provides the two-inch straight pipe threads once those threads become damaged. The drum filler or reconditioner simply removes the closure with a special removal tool and then crimps on a new closure with a suitable crimping tool.
While the closure art is quite crowded, the types of closures can generally be classified as to their features and/or applications. Considering one such classification as including closures which are internally threaded, crimped to a drum neck opening and which use a removable plug for closing the central opening of the closure, the following references are believed to be of interest as a sampling of what is known in the art in this particular classification.
______________________________________ Pat. No. Patentee ______________________________________ 3,179,280 Littlefield 4,114,779 Stoll, III 3,684,125 Laurizio 3,958,719 Ward 3,747,962 Bauman 4,195,750 Fee 3,098,579 Wheaton 3,080,182 Waldo 2,842,282 Parish 3,437,226 Helwig ______________________________________
Littlefield discloses a closure for containers wherein an internally threaded plastic closure is secured to the raised metal boss of a drum end opening by means of a crimping ring. To the extent that this reference discloses a plastic closure secured to a drum end, it is relevant. However, the fact that the crimping ring is disposed within the plastic closure and is actually deformed and crimped into and against the raised metal boss of the drum end results in this particular closure being nonremovable in a manner that would allow a new closure to be installed by the filler or reconditioner. The crimping procedure disclosed in Littlefield actually deforms the neck finish of the drum end thereby precluding a repeat of the assembly process.
Stoll, III discloses a closure assembly for plastic drums wherein a tubular projection of the drum head is formed with buttress threads and the closure includes an adapter having external buttress threads for engagement with tubular projection and internal standard pipe threads in order to receive standard pipe threaded members such as dispensing valves, pump fittings, as well as standard bung plugs. The particular design disclosed in Stoll does not include a retaining ring which secures the closure into the drum end. As a result the structure disclosed by Stoll is not believed to provide the necessary strength and durability required for retention of the closure in its desired location and orientation. An additional concern with this type of design is that there is now one additional interface through which contents of the drum may leak. One benefit of having a crimped-on outer retaining ring which conforms a portion of the internally threaded flange to the neck finish is that there is provided a liquid-tight interface. That particular interface is not provided by the design of Stoll.
Laurizio discloses a container closure assembly which includes a synthetic plastic closure flange, a closure plug and an overlying synthetic plastic cap seal which includes a metal securing ring. In Laurizio, the retaining ring is joined to the outer portion of the overseal, and while it is used to crimp the overseal against the internally threaded plastic flange, there appears to be very little crimping strength provided inasmuch as the metal retaining ring does not extend axially on both sides of the raised neck finish of the drum end. Consequently, any crimping force must be controlled so as not to distort or break any portions of the plastic flange or neck finish. In the present invention, the retaining ring used is of a wrap-around design such that it provides a suitable back-up support for the crimping operation such that the outer, radially extending lip of the internally threaded plastic closure can be tightly crimped to the neck finish without risking any distortion or damage to the remainder of the closure. Another aspect of the present invention is the presence of internal splines as part of the neck finish and cooperating external splines on the outside diameter surface of the internally threaded plastic flange. The mating engagement of these internal and external splines strengthens the overall closure against movement under torque and rotation as threaded members may be inserted and removed during filling and dispensing operation.
The structure of Laurizio does not disclose such splines and the general impression formed is of a low-strength closure wherein the plastic flange merely snaps over an enlarged head portion of the neck finish of the drum end and thereafter the retaining ring is lightly crimped in order to hold the snap fit together. This snap-fit concept and the fact that the flange of Laurizio is not actually crimped around the neck finish is evident from the matching shapes of neck finish 3 and the receiving recess of sealing portion 9.
Ward discloses a container for fluids which includes a cap and a coupling member which is interposed between the neck of the container and the cap which is fitted to the container after it has been formed. The coupling member is readily attachable to the container from its exterior without requiring any modification to the container or other components. This particular design is generally a snap-in type of fit not involving either a splined neck finish nor a metal crimping ring. The particular design is not believed to be designed for use with plastic drums, nor does it appear to have the requisite strength and resistance to torque which would be necessary for receiving and functioning properly with various filling and dispensing equipment which must be threadedly received by the internal threads of the closure.
Bauman, Fee and Parish while arguably somewhat relevant to the present invention, possess one characteristic which makes their design completely unacceptable as a means of complying with the teachings of the present invention. Each of these three designs require insertion of and assembly of the plastic closure from inside of the drum, moving from the inside to the outside. In order to make these types of closure assemblies, it is necessary that the closure be assembled to the drum end prior to completing the fabrication of the drum. Consequently, although each of these references do disclose some type of closure which is secured to a neck finish of a drum end, the particular geometry of each plastic closure necessitates that it be inserted from the inside of the container in an outward direction. This is only possible prior to fabrication of the container and would thus not be an acceptable design for a closure which is designed for and intended to be replaced by fillers and reconditioners. As used herein, the term "filler" means the customer for the container manufacturer, and the term "reconditioner" is one who purchases used containers and sells these back to the fillers.
Wheaton discloses a closure design which is intended for restoring drums (steel barrels) to a leak-proof condition once its particular gaskets have been rendered ineffective by the heat employed in the reconditioning of steel drums. However, the Wheaton design does nothing to restore the thread condition, it is only directed to the gasket/sealing problem. This particular design also fits within the same category of Bauman, Fee and Parish wherein the closure must be inserted through the drum end, from inside of the drum in an outward direction. After such insertion, the top margin of the closure is beaded over the neck of the drum end (6). The particular invention of Wheaton is directed to the addition of auxiliary gaskets in order to reestablish a leak-proof condition once that condition has deteriorated. Again, as with the foregoing group of references, the plastic closure is not designed as a replaceable unit, which is in fact the primary purpose of the present invention.
Waldo discloses a container closure wherein an annular slot is provided in the undersurface of the closure and is designed and arranged to fit over a generally cylindrical raised wall formed in the drum end. An externally threaded plug is used to close the central opening in the closure flange and a cap seal is crimped in place covering both the plug and the closure flange as a final securing and sealing means for storage and shipment. Based upon the design of the disclosed flange and the shape and style of the drum neck finish, it is clear that this particular structure is not suitable for a drum opening which will be subjected to high levels of torque in the installing and removing of various threaded fittings for the filling and dispensing of the container contents. Additionally, the neck finish is straight and cylindrical and the closure flange actually rises above the drum end rather than being received down inside of the drum end. There is thus some question as to this raised height and its suitability for shipment and storage, wherein the present invention provides a much lower profile configuration.
Helwig discloses a plastic closure flange assembly which is attached to a raised metal boss of a drum end by means of an annular retaining ring which is actually received by the plastic closure. This particular design concept is not intended to provide a removable/replaceable flange. Rather, the flange assembly of Helwig is to be permanently secured to the above-described opening formation by placing the flange seal lip thereover and forming the securing ring leg 23 radially inwardly adjacent its lower edge so as to pinch the lowermost end 14 of the lip outer wall 13 against the free edge 54 and cause the plastic material to be squeezed therebetween as shown (column 3, lines 11-18). In order to achieve the desired degree of securement and the compression of the plastic material against extending portion 53, that portion is deformed during the crimping operation. Thus, even if it was possible to remove the plastic closure from the drum neck finish, replacement and reassembly of a new closure member would be quite difficult since the available degree of tightening and compression, and the actual deformation of portion 53 will have previously occurred, it will be difficult, if not impossible, to reestablish the requisite seal at that component interface. With the present invention, there is no deformation nor any distortion of the drum end neck finish.
In fact, one characteristic of a plastic drum as opposed to a metal drum is the wall thickness which is present and the ability to mold the drum material into various shapes and contours. By providing a drum end neck finish with substantial wall thickness, that particular portion of the drum end can be made very durable and unyielding. Since the outer lip of the flange of the present invention, which is crimped around the neck finish, is of a thinner cross-sectional dimension than the neck finish, it is thus more deformable. Finally, as is taught by the present invention, by shaping the retaining ring such that it extends on both sides of the neck finish, very tight and secure crimping is possible without deforming or altering any other portion of the closure and without affecting nor altering the neck finish such that its shape remains constant. By allowing that neck finish shape to remain unaffected, it is always available in the same location and with the same contour for the assembly thereto of replacement closures.
Although several of the listed patent references which have been discussed above disclose closures which include a crimping ring, a closing plug and an internally threaded opening, the present invention provides a unique design which is specifically styled for replacement of the closure. The particular shape and contour of the component parts of the present invention enable removal of the closure while still preserving the drum and its neck finish appearance thereby permitting new closures to be installed and recycling of the drum even though the original closure threads may be damaged.